Method and apparatus for joining the ends of aluminum conductors by castwelding

ABSTRACT

The ends of large aluminum conductors are confined in juxtaposition in a preheated mold. in an inert atmosphere molten aluminum is first caused to flow across the exposed ends of the conductors, remove impurities, and is thereafter confined to surround and join the end portions of the conductors at which time it is solidified.

United States Patent McMurray et al.

1451 Jan. 14, 1975 [54] METHOD AND APPARATUS FOR JOINING THE ENDS 0FALUMINUM CONDUCTORS BY CASTWELDING Inventors: William C. McMurray, St.Clair Shores; Mitchell D. Charneski, Southfield, both of Mich.

The Detroit Edison Company, Detroit, Mich.

Filed: Jan. 2, 1973 Appl. No.: 320,105

Assignee:

[52] US. Cl 164/333, 164/108, 164/334, 164/337, 164/338, 249/78, 249/79,249/94, 249/95, 249/97 Int. Cl B22d 37/00 Field of Search 164/335, 338,333, 334, 164/337, 332, 108, DIG. 12, 112, 103, 105, 98, 100, 250;249/97, 78, 79, 96, 83, 90, 93, 94, 95, 85, 86, 91

References Cited UNITED STATES PATENTS 2/1930 Bottrill 249/96 X1,838,357 12/1931 Bottrill 164/DIG. 12 2,171,778 9/1939 Yantis 164/335 X3,004,310 10/1961 Burke 249/96 3,233,292 2/1966 Kramer et a1 164/108 XFOREIGN PATENTS OR APPLICATIONS 948,354 1/1949 France 164/108 PrimaryExaminer-Francis S. Husar Assistant Examiner-V. K. Rising Attorney,Agent, or Firm-Whittemore, Hulbert & Belknap [5 7 ABSTRACT The ends oflarge aluminum conductors are confined in juxtaposition in a preheatedmold. in an inert atmosphere molten aluminum is first caused to flowacross the exposed ends of the conductors, remove impurities, and isthereafter confined to surround and join the end portions of theconductors at which time it is solidified.

4 Claims, 3 Drawing Figures METHOD AND APPARATUS FOR JOINING THE ENDS OFALUMINUM CONDUCTORS BY CASTWELDING BRIEF SUMMARY OF THE INVENTION Thepresent invention relates to a method and apparatus for economicallyjoining the ends of large aluminum conductors by castwelding. Theinvention isapplicable to either clean conductors or conductors whichmay be covered with oil or which may include multiple strands with oilwithin the conductor. The invention produces a metallurgical bond ofhigh electrical conductivity and high tensile strength.

The castwelding is accomplished by first melting an electrical gradealuminum in a portable furnace with the aluminum protected fromoxidation-(argon or another inert gas). Then the molten aluminum ischanneled into a preheated mold containing the bared connector endspositioned in juxtaposition to each other. While the mold cavity isunder the same protective atmosphere, the molten aluminum is directedagainst the end faces of the conductors contained therein. Impingementof the melted aluminum cleans the oxide and oils from the conductor endsso that a fusion or metallurgical bond of the aluminum conductors andmelted metal is caused to occur. The temperature of the molten aluminumis sufficiently high so that it will produce at least some melting ofthe surface portions of the aluminum cable, thus causing the impuritiesand contaminants to flow away from the bared conductor ends.

All heating of the aluminum which constitutes the joint is done outsidethe weld zone, thus only the minimum heat necessary to melt the requiredamount of aluminum for the joint, plus a small amount of surplus heat tomelt part of the strands, and to compensate for slight losses, isrequired. The cable therefore requires minimum cooling after thecastweld operation.

Cooling clamps are attached to the cable on each side of the mold tolimit conduction of heat from the mold and thereby to maintaintemperatures within the conductor exterior of the mold belowtemperatures which would be deleterious to conductor insulation The moldand cooling clamps may be cooled by controlled circulation of compressedair or CO BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectionthrough the apparatus.

FIG. 2 is a vertical section taken 90 from the sectional view of FIG. 1.

FIG. 3 is an elevational view of the front of the control console.

DETAILED DESCRIPTION FIGS. 1 and 2 illustrate the apparatus as appliedto producing a castweld joint in a four-sector compact strand aluminumconductor having an outside diameter of approximately 1%. inch. It willthus be seen that the apparatus is extremely compact and that forproducing a castweld joint on large aluminum cable of this size the.overall height of the apparatus is only slightly over 14 inches.

The apparatus thus is quite small and readily portable, and hasextremely useful characteristics of a device for making joints inconfined spaces such as manholes.

Moreover, as will subsequently be described in detail, the furnace powerfor melting the aluminum is supplied from electrical resistance heatingelements operable on low commercial voltages such for example as 220volts, thus providing a safety factor where the apparatus is used indamp or wet confined spaces such as manholes.

The aluminum is melted in a portable furnace indicated generally at 10which comprises a carbon crucible l2 surrounded by high temperatureinsulation 14 such as aluminum silicate surrounded by a stainless steeljacket 16. Preferably, the stainless steel jacket is surrounded orpartly surrounded by a rugged metal screen 18 spaced at a small distancefrom the steel jacket to provide an air space and to allow the user tohandle the pot, should the need arise, even after it has reached maximumtemperature.

An opening 20 is provided at the bottom of the crucible 12 and flow ofmolten aluminum through the opening 20 is controlled by a carbon gate 22having a port 24 adapted to be moved in registration with the elongatedopening 20 by suitable actuating means such for example as a solenoidindicated generally at 26. When energized, the solenoid is adapted toshift the port 24 into registration with the opening 20 and to permitmolten aluminum to flow downwardly out of the carbon crucible 12.Suitable means such for example as a spring (not shown) is provided formoving the gate 22 to the closing position illustrated in FIG. 2.

Directly adjacent the outer surface of the carbon crucible 12 areheating means 28 which include electrical resistance heating elements30.

Means are provided for evacuating air from the furnace and this means isindicated as a conduit 32 for forcing argon or another inert gas intothe furnace to evacuate air therefrom.

Means are provided for sensing the temperature of the aluminum in thecrucible and this means is shown as a thermocouple 34 embedded in thecarbon crucible and having an external connection 36 to suitableautomatic control means responsive to temperature of the aluminum in thecrucible.

Below the furnace 10 is a mold assembly indicated in its entirety at 40and comprising a steel mold 42 having a horizontal through opening 44intersecting a vertical through opening 46. The lower end of the throughopening 46 is provided with a closure 48 dividing the verticallyextending through opening 46 into a mold well 50, a riser passage 52,and intermediate the mold well and riser passage, the mold cavity 54which surrounds the ends of the aluminum electrical conductors 56. Thehorizontally extending opening 44 is slightly larger than the diameterof the conductors 56 and receives collars 58 which limit flow of moltenaluminum longitudinally of the cable from the intermediate portion ofthe mold cavity 54.

In the specific construction illustrated the collars 58 may have a wallthickness of approximately 5/32 inches, and the inner ends thereof maybe spaced approximately l%inches from the vertical opening 46.

A connection 59 is provided for causing an inert gas such for example asargon to flow into the mold and to displace air from the mold so thatthe formation of the castweld may take place in an inert atmosphere.

The steel mold 42 is provided with electrical resis tance heatingelements 60 having external connections indicated at 62 for the purposeof preheating the mold and the ends of the conductor therein to atemperature slightly below the melting temperature of aluminum. Thesteel mold 42 is further provided with passages diagrammaticallyindicated at 64 through which cooling fluid may be circulated followingpouring of the molten aluminum. The cooling fluid may be air, CO or thelike.

The steel mold 42 is surrounded by high temperature insulation 66 suchfor example as aluminum silicate surrounded by a steel jacket 68.

The furnace and the mold assembly 40 are interconnected by flangedtubular portions indicated generally at 70 suitably secured together asfor example by screws 72.

It will be appreciated of course that the mold assembly 40 must beformed in two pieces to permit removal of the castweld joint followingsolidification of the molten metal, and this arrangement is indicateddiagram matically by the partition line 74.

Means 76 provide a local cooling action to the portions of theconductors directly adjacent the exterior of the mold assembly 40. Thismeans comprises a twopiece removable cooling clamp having connections78and 80 for circulating a cooling fluid such for example as air, C0,, orthe like.

The furnace 10 includes a sealing and insulating cover 82 including aninsulating core 84 surrounded by a steel shell 86. The cover is adaptedto be clamped in closing position at the upper end of the furnace bysuitable means such, for example, as screws 88, apertured ears 90, andwing nuts 92.

In use the ends of the electricalconductors 46 are preferably beveled asindicated at 94 and the beveled surfaces are positioned to be exposedupwardly to cause molten aluminum discharged from thecrucible 12 to flowacross the beveled surfaces. In order to produce the most effective flowof molten aluminum, the lower end of the crucible, below the gate 22, isprovided with a pour spout 96 having two nozzles 98 each of which isprovided with an elongated passage for directing molten aluminum to oneof the beveled surfaces 94. Accordingly, the pour spout divides the flowof molten aluminum into two paths each of which is directed to one ofthe beveled surfaces of the cable 56.

The steel molds 42 are designed to do five things: First, the electricheating elements in the mold preheat the mold and cable parts prior tothe pouring operation. Secondly, the well of the mold permits asubstantial flow of molten aluminum across the ends of the aluminumconductor and provides a space for storage of the surplus aluminumtogether with the contained contaminants below the cable ends tofacilitate the making of a castweld joint between clean cable ends.Third, the provision of mold space of slightly larger diameter than thatof the cable around the cable ends aids in preheating the conductor andpermits the solidified metal to grip the cable strands inwardly from theend and outer surfaces for additional tensile strength. Fourth, passagesin the mold provide for flow of coolant in properly timed relation inthe cooling cycle to achieve a desirable fine grain (equi-axed)structure. Fifth, risers of proper size plus the preheat and operationalprocedures eliminate the common defects associated with casting orwelding of aluminum. Such defects which have been eliminated by thepresent method and apparatus are shrink holes, gas pockets, shrinkcracks, large grain size, and poor interface weld. Accordingly, there isa consequent increase in aluminum purity, strength,

and conductivity. ,g

The cooling clampsindicatedat 76 are designed to feed compressed air orCO gas across and around the cable strands, and are not designed to actas conductive cooling fins. For this reason they may be made of anyrugged material capable of withstanding about 300 F. continuously. I

The apparatus as described in the foregoing may be operated manually,but in order to insure that an inexperienced splicer may obtain perfectwelds each time, it is preferred to automate the operation.

In FIG. 3 there is illustrated a control console 100. Within the consoleare the valves and switches necessary to perform automatic cycling ofthe apparatus. As illustrated, the console includes an inlet connection102 and an outlet connection 104 for inert gas such as argon. An inletconnection 106 is provided for compressed air or CO and outletconnections 108 and 110 are provided for supplying the cooling fluid tothe cooling clamps 76 and the cooling passages 64 of the steel mold 42.Input electrical connection means 112 are provided. An outlet fitting114 is provided for connection of the heating current to the electricalheating elements 28'and 60. A fitting 116 is provided for connection tothe thermocouple.

A main ON and OFF switch 118 is provided and a selector switch 120 isprovided for selecting either manual or automatic control.

For manual control the appropriate switches are provided with manuallyoperable actuators and these switches are indicated at 122, 124, 126,128 and 130. Associated with each of the switches is a signal light 132which may be of appropriately different colors. For example, the switch122 may supply current to the heating elements 28, and if desired, asimilar but separate switch (not shown) may be provided for controllingthe circuit to the heating element 60 provided in the mold 42. Actuationof the solenoid 26 may be under the control of the switch 124. Theswitch 126 controls the flow .of coolant to the cooling clamps 76, andthe switch 128 controls flow of coolant to the cooling passages 64 inthe mold. The switch 130 terminates the cycle. I

With the switch 120 in the position to select automatic operation,current is supplied to heating elements 28 and the temperature is sensedby the thermocouple 34. When the temperature has risen a predeterminedamount, or when a predetermined time interval has passed, the switchsupplying current to the mold heating elements 60 is closed. When thealuminum has been completely melted and attained the proper temperatureas sensed by the thermocouple, the solenoid 26 is energized actuatingthe gate valve and permitting 7 the melted aluminum to flow downwardlyand be divided by the pour spout into two. streams, each of which flowsacross the exposed end surface of the aluminum cables, carrying away theoxide at the surface and any impurities or contaminants which may bepresent. These are trapped within the mold well and as the pouringoperation continues, the pure molten aluminum rises across the endsurface of the conductors and enters the riser passage 52. At this timethe switch 126 is operated to direct flow of coolant through the coolingclamps 76 and shortly thereafter, the switch 128 is operated to directcoolant to the passages 64 within the mold 42. The heating elements 28and 62 are of course de-energized by operation of the switchescontrolling the current thereto at the appropriate point in the cycle.As soon as the mold has cooled sufficiently the operation is completeand the cables with the castweld joint are removed from the mold. Atthis time the lateral projections formed by the solidified material inthe mold well and in the riser passage may be mechanically removed.

In the foregoing it has been implied that the quantity of aluminummelted in the pot is that amount which is required for the production ofa single weld. The invention however, contemplates the possibility thatthe pot may be substantially enlarged and the cycle changed to maintaina supply of molten aluminum within the crucible as a plurality ofcastwelds are made. This requires that the timing of the operation ofthe carbon gate 22 shall be such as to meter a measured amount of moltenaluminum into the mold. With this operation a number of joints may beproduced in a shortened time since the time cycle will not requiremelting of a charge of aluminum for each operation.

There are many advantages in the method and apparatus disclosed herein.In the first place, substantial economies are achieved because ofinexpensive equipment. The apparatus is simple and can be operated byinexperienced splicers. The operation is very fast operating includingthe time cycle required for melting the aluminum and the time cycle forsolidification. of the cast metal, all of which permits the productionof multiple splices.

Since the castweld is produced by high purity electrical grade aluminummelted in an inert atmosphere in an operation which substantiallyeliminates contaminants from within the weld zone, the joints have highelectrical conductors and produce a bond superior to previously knownmethods. As a consequence, the joints have high tensile strength andallow long pulls of conductors between separated manholes. The jointsare corrosion resistant since they are made of electrical grade aluminumas is the conductor.

Since the operation as described, is effective to carry away oil orother contaminants which may be present at and adjacent the ends of thecables, the operation requires no solvents or water.

A very important advantage of the apparatus and method disclosed hereinis its low power requirements.

The foregoing advantages become particularly apparent when compared withtwo prior welding methods which have some times been used. The priorwelding methods are: The inert-gas arc welding method, and inductionwelding. The inert-gas arc welding method suffers from the tediousrequirement of cleaning with solvents even the slightest traces of oilfrom the conductor in order to obtain a useful bond. Tensile strengthsare as low as one-third of the breaking strength of the cable. The useof solvents in a manhole of restricted space pose obvious hazards.Furthermore, the arc welding method requires the services of twospecially trained welders with costly equipment.

Induction welding as applied to cables of the type disclosed herein,requires about 100 kva of instantaneous power plus a cooling watersupply. These are highly undesirable requirements, particularly incarrying out the induction welding in manholes where problems areencountered as a result of the use of extremely heavy and bulkytransformer equipment.

The castweld system appears to have significant advantages in everyaspect of its application and use. What we claim as our invention is:

1. Apparatus for castweld joining of large aluminum conductors whichcomprises an insulated pot for melting a charge of aluminum, heatingmeans incorporated into the pot, said pot having a gate-controlledopening at the bottom thereof, a mold directly below the bottom openingin said pot, said mold having a mold cavity for receiving the bared endsof two conductors to be joined by castwelding, a well extendingdownwardly from said cavity, means for locating the conductor ends inposition such that melted aluminum discharged from said pot flows overthem and into said well, and a riser passage extending upwardly fromsaid mold cavity, in which said heating means comprises electricalresistance heating elements operable at low commercial voltages to meltaluminum in said pot, said mold cavity being defined by the intersectionof a vertical cylindrical opening, the lower portion of which forms saidwell and the upper portion of which forms said riser passage, and ahorizontal cylindrical opening, the portions of which adjacent saidvertical opening are slightly larger than the conductors to be joined toprovide for a flow of melted aluminum along the outer surface of saidconductors, said mold comprising a two-piece metal block having saidhorizontal and vertical openings therein, the division between the twopieces of said block being in a vertical plane bisecting said horizontaland vertical openings, and mold preheating means comprising low voltageelectric heating elements incorporated therein, said mold having moldcooling means comprising flow passages therein for receiving a fluidcoolant to accelerate solidification of molten aluminum after pouringthe molten aluminum into said mold, and means for circulating thecoolant through said flow passages.

2. Apparatus for castweld joining of large aluminum conductors whichcomprises an insulated pot for melting a charge of aluminum, heatingmeans incorporated into the pot, said pot having a gate-controlledopening at the bottom thereof, a mold directly below the bottom openingin said pot, said mold having a mold cavity for receiving the bared endsof two conductors to be joined by castwelding, a well extendingdownwardly from said cavity, means for locating the conductor ends inposition such that melted aluminum discharged from said pot flows overthem and into said well, and a riser passage extending upwardly fromsaid mold cavity, comprising in addition means for dividing the flow ofmolten aluminum into two parts, and directing each part against the endsof one of the conductors.

3. Apparatus as defined in claim 2 comprising means for supporting theconductor ends in spaced relation.

4. Apparatus for castweld joining of aluminum conductors which comprisesa mold having a cavity for re ceiving the ends of horizontally disposedaluminum conductors in proximity to each other, a well disposed beneathsaid cavity to receive melted metal flowing downwardly through saidcavity over the proximate surfaces of the conductors, said mold having ahorizontally extending opening therethrough intersecting said moldcavity, the outer portions of said opening dimensioned to closelyembrace portions of conductors received therein, the portions of saidopening adjacent said mold cavity being slightly enlarged to provideannular chambers dimensioned to permit a flow of molten aluminum intosaid chambers and to surround portions of said conductors adjacent theends thereof, a riser passage extending upwardly from said cavity tochannel a flow of melted metal into said cavity and to receive metal tosaid riser passage, said mold cavity having low voltage electricalresistance heating elements incorporated therein and in addition having;passages for the circulation of cooling fluids therethrough to controlthe excess melted metal after said cavity and well are filled, coolingcycle of melted metal therein.

and means for supplying controlled amounts of melted

1. Apparatus for castweld joining of large aluminum conductors whichcomprises an insulated pot for melting a charge of aluminum, heatingmeans incorporated into the pot, said pot having a gate-controlledopening at the bottom thereof, a mold directly below the bottom openingin said pot, said mold having a mold cavity for receiving the bared endsof two conductors to be joined by castwelding, a well extendingdownwardly from said cavity, means for locating the conductor ends inposition such that melted aluminum discharged from said pot flows overthem and into said well, and a riser passage extending upwardly fromsaid mold cavity, in which said heating means comprises electricalresistance heating elements operable at low commercial voltages to meltaluminum in said pot, said mold cavity being defined by the intersectionof a vertical cylindrical opening, the lower portion of which forms saidwell and the upper portion of which forms said riser passage, and ahorizontal cylindrical opening, the portions of which adjacent saidvertical opening are slightly larger than the conductors to be joined toprovide for a flow of melted aluminum along the outer surface of saidconductors, said mold comprising a two-piece metal block having saidhorizontal and vertical openings therein, the division between the twopieces of said block being in a vertical plane bisecting said horizontaland vertical openings, and mold preheating means comprising low voltageelectric heating elements incorporated therein, said mold having moldcooling means comprising flow passages therein for receiving a fluidcoolant to accelerate solidification of molten aluminum after pouringthe molten aluminum into said mold, and means for circulating thecoolant through said flow passages.
 2. Apparatus for castweld joining oflarge aluminum conductors which comprises an insulated pot for melting acharge of aluminum, heating means incorporated into the pot, said pothaving a gate-controlled opening aT the bottom thereof, a mold directlybelow the bottom opening in said pot, said mold having a mold cavity forreceiving the bared ends of two conductors to be joined by castwelding,a well extending downwardly from said cavity, means for locating theconductor ends in position such that melted aluminum discharged fromsaid pot flows over them and into said well, and a riser passageextending upwardly from said mold cavity, comprising in addition meansfor dividing the flow of molten aluminum into two parts, and directingeach part against the ends of one of the conductors.
 3. Apparatus asdefined in claim 2 comprising means for supporting the conductor ends inspaced relation.
 4. Apparatus for castweld joining of aluminumconductors which comprises a mold having a cavity for receiving the endsof horizontally disposed aluminum conductors in proximity to each other,a well disposed beneath said cavity to receive melted metal flowingdownwardly through said cavity over the proximate surfaces of theconductors, said mold having a horizontally extending openingtherethrough intersecting said mold cavity, the outer portions of saidopening dimensioned to closely embrace portions of conductors receivedtherein, the portions of said opening adjacent said mold cavity beingslightly enlarged to provide annular chambers dimensioned to permit aflow of molten aluminum into said chambers and to surround portions ofsaid conductors adjacent the ends thereof, a riser passage extendingupwardly from said cavity to channel a flow of melted metal into saidcavity and to receive excess melted metal after said cavity and well arefilled, and means for supplying controlled amounts of melted metal tosaid riser passage, said mold cavity having low voltage electricalresistance heating elements incorporated therein and in addition havingpassages for the circulation of cooling fluids therethrough to controlthe cooling cycle of melted metal therein.